Printing plate preparation



Dec. 3, 1968 R. A. SHADE ET AL 3,413,706

PRINTING PLATE PREPARATION Filed May 11, 1964 3 Sheets-Sheet 1 Dec. 3, 1968 R. A. SHADE ET AL PRINTING PLATE PREPARATION Filed May 11, 1964 5 Sheets-Sheet 2 Q fili l/Z2 0] ff 1%i/Zi7f9/5MW n EZ'bA f 0/41 [lag/MW;

Dec. 3, 1968 SHADE ET AL PRINTING PLATE PREPARATION 3 Sheets-Sheet 3 Filed May 11, 1964 6 022%! 66%?124/ (1 1 Zw y/wa 2a United States Patent 3,413,706 PRINTING PLATE PREPARATION Robert Allen Shade, Ernst Daniel Nystrand, and Gerald Lee Marchant, Green Bay, Wis., assignors to Paper Converting Machine Co., Inc., Green Bay, Wis., a corporation of Wisconsin Filed May 11, 1964, Ser. No. 366,372 3 Claims. (Cl. 29-407) This invention relates to a printing plate preparation, including the method of the same. More particularly, the invention relates to the preparation of flexible plastic plates which are wrapped around a plate cylinder.

This application is related to the copending, co-owned application of Ernst D. Nystrand, Ser. No. 327,711 filed Dec. 3, 1963, now Patent No. 3,195,458, and reference may be had to that application for additional particulars of the printing apparatus in which the plate prepared according to the instant invention is used.

One important use of plastic printing plates is in the production of multiple copy forms wherein a plurality of identical plates are employed to simultaneously print a plurality of webs, which are then arranged in register for the development of the multiple copy formsas for a variety of office procedures. The above-mentioned Nystrand application has to do with structure for mount ing a film-type plate in the printing press. In doing this, however, it was found that the plates were not uniformly stressed, so that perfect register in the various Webs was not achieved. Therefore, an important objective of the instant invention is to provide a method and apparatus for preparing thin plastic film printing plates in such a fashion that the same are advantageously mounted on plate cylinders so as to avoid the undesirable feature of imperfect register in going from one printing plate to another.

Another object of the invention is to provide a method of preparing printing plates of the thin flexible type which are intended to be installed on plate cylinders and which further are advantageously used in multiple copy form printing, such printing requiring a minimal gap between repeats, i.e., gaps exceeding about one-half inch between repeats being unacceptable.

Other objects and advantages of the invention may be seen in the details of construction and operation set down in this specification.

The invention is explained in conjunction with the accompanying drawing, in which:

FIG. 1 is a fragmentary top plan view of a printing plate mounting apparatus embodying teachings of the invention;

FIG. 2 is a longitudinal vertical sectional view through the apparatus as taken along the line 22 of FIG. 1;

FIGS. 3 and 4 reflect detail sectional views through FIG. 2 as along the lines 33 and 44, respectively of FIG. 2;

FIG. 5 is a perspective view of the structure of FIGS. 1 and 2 and illustrating the manner of locating the printing plate thereon;

FIG. 6 is a top plan view of the structure, showing how the located plate of FIG. 5 is clamped at one end by a clamping bar and at the other end by stretching weights and which will be more fully described hereinafter;

FIG. 7 is a perspective view showing how the structure is disposed in a vertical position so that the weights exert an even tensioning stress on the plate and the second clamping bar is tightened;

FIG. 8 is a perspective view of the structure, showing how the plate is scribed, for future bending, using the clamping bars as guides in this operation;

FIG. 9 is a side view of the plate after it has been scribed as in FIG. 8;

FIG. 10 is a perspective view of the structure which may be employed for trimming and scoring the plate after the scribing operation described above has been performed;

FIG. 11 is a schematic perspective view, showing how the scribed ends of the sheet may be heated to make the same suitable for creasing;

FIG. 12 is a perspective view showing one way in which the end margins of the plates may be bent over and creased after the heating operation of FIG. 11;

FIG. 13 is an end view of the plate after the creasing in FIG. 12 and arranged in cylindrical form;

FIG. 14 shows the finished plate when mounted on the plaie cylinder of a press; and

FIG. 15 is an elevational view of a stand upon which the structure of FIGS. 1 and 2 is mounted for turning the same at different angular positions for handling the plate.

In the illustration given and with particular reference to FIG. 14, the numeral designates a plate cylinder which is suitably equipped with a shaft 21 permitting the same to be rotatably mounted in a printing press (not shown). The numeral 22 designates generally the printing plate (see also FIG. 13), which is to be prepared according to this invention. A dovetail slot as at 23 is provided in the plate cylinder 20, and the method of mounting the plate 22 therein, along with the clamping members 24.

and 25, is described in detail in the above-mentioned Nystrand application.

In preparing a plate for this installation, excellent results are obtained when dyacril plates, marketed by E. I. duPont de Nemours & Co., are employed, such plates having a photosensitive, etchable coating thereon backed by a plastic supporting layer identified as Kronar.

Referring now to FIG. 2, it is seen that apparatus for preparing the plate includes a frame or base 26 which provides a planar or flat platform 27. The frame 26 pro vides a support for a first clamping member 28 (see FIG. 4) adjacent and over one end of the platform 27. The clamping bar 28 is seen to confine one edge of the plate 22, and for this purpose the clamping bar 28 is secured to the plafol'rn 27 by means of a capscrew or bolt 30, about which is ensleeved a spring 29.

A second clamping bar or member 31 is provided at the other end of the platform 27, and this clamping bar is also provided with a plurality of capscrews 33, each equipped with its helical spring 32.

Freely supported on the frame 26 at one end of the platform 27 are a plurality of weights 34 made up of upper and lower portions 35 and 36, respectively (see FIG. 2). The upper and lower parts 35 and 36 are connected together by means of capscrews 27, each being equipped with springs 38.

Referring now to FIG. 5, the first step in preparing the plate 22 is to position the same on the platform 27, and in FIG. 5 we see a scale or rule 39 in the hand of an operator 40 being used to position a reference mark 41 a predetermined distance from the linear edge of the first clamping bar 28. This provides a point of reference'which will be identical for each of the multiplicity of plates 22 which will be provided according to the instant invention.

Now referring to FIG. 6, a wrench 42 is employed to tighten each of the capscrews 30 against the urging of the associated springs 29 so that one end of the plate 22 is secured to the platform 27 in the fashion shown in FIG. 4.

Following the clamping operation illustrated in FIG. 6, a second clamping operation is also performed, and this also is depicted somewhat schematically in FIG. 6, wherein a wrench 43 is employed to tighten the capscrews 37 associated with the various weights 34. As a result of these two clamping operations, the plate 22 is clamped along one end by the first clamping bar 28 and is thus immovable at that end relative to the platform 27. The other end of the plate 22, i.e., the end engaged by the plurality of weights 34, is free to move relative to the platform, and the weights 34 exert a uniform tension stress across the width of the plate 22. The uniform stress is advantageously utilized by orienting the platform vertically in the condition illustrated in FIG. 7, whereby the weights 34 extending across the width of the plate 22 elongate the same within its elastic limit and provide reproducible results in working on successive plates 22.

While the plate 22 is under the stress illustrated in FIG. 7, a wrench 44 is employed to tighten the capscrews 33 associated with the second clamping bar 31. This is performed in the illustration given-while the platform 27 is vertically oriented so that now the plate 22 is confined between two straight edge-equipped, parallel clamping bars 28 and 31.

Following the operation pictured in FIG. 7, the plate 22 is suitably scribed as is illustrated schematically in FIG. 8 wherein the operator 40 makes use of a stylus 45 for drawing a line along the plate 22 using the first clamping bar as a guide. A similar scribe line is developed by drawing the stylus along the second clamping bar 31. After this has been achieved, the various clamps and weights are released to provide the plate in the form seen in FIG. 9, wherein the first scribe mark is designated by the numeral 46 and the second by the numeral 47-it being seen that the plate 22 extends a greater distance beyond the scribe line 47 than beyond the line 46-as at 48. In the illustration given, this is advantageous, since it provides an additional edge portion for connection of the weights 34. In FIG. 10, a knife-equipped cutting board is designated 49 and the knife 50 is seen in the process of trimming the excess edge portion 48 from the plate 22.

Thereafter, according to the invention, the plate 22 is heated-advantageously to a temperature in the range of IOU-200 F. and in areas along the scribe lines 46 and 47 by means of a suitable heater as at 51 which facilitates the creasing operation shown in FIG. 12.

In FIG. 12, the plate 22 is seen being creased along the line 46 as by a suitable creasing roller 52, after which the same operation is performed along the line 47 to develop the construction seen in FIG. 13. In FIG. 13, the creases are again designated as at 46 and 47 and provide radially inwardly-extending folded edges as at 46a and 47a which are advantageously clamped within the dovetailed recess 23 of the plate cylinder 20.

It will be appreciated that the platform 27 may be advantageously mounted on a swivel joint as at 53 (see FIG. so as to facilitate the reorientation to the vertical position designated 27' in FIG. 15, thereby applying the uniform longitudinal stress to the plate 22 illustrated schematically in FIG. 7.

The printing plate mounting system has advantageous application to thin wrap-around printing plates employed for mounting on plate cylinders. The printing plate material may be magnesium, zinc, metal-backed rubber, metal-backed photopolymer, metal-backed tanned gelatin, aluminum, or plastic-backed plates of any of these materials. Summarizing, the steps involved in preparing the plates include:

(1) Clamping one end of the plate in a fixture; orienting the plate to the clamping device by referring the image to the clamp;

(2) Applying tension to the opposite end of the plate in a uniform manner. The illustrated method of doing this is to apply weights to the opposite end of the plate and orient the fixture so that gravity exerts a constant tension across the entire width of the plate. The weights are such that they approach but do not exceed the yield limit of the plate material.

(3) While tension is exerted across the width of the plate, a second clamping device is applied to the end opposite the first clamping device and thereby hold the plate on two of its four sides.

(4) Next a scribe line is placed across both clamped edges, using the straight edges of the clamps as a guide, thereby providing scribe lines suitably referred to the image, it being appreciated that the clamping members are arranged in parallel relation to each other.

(5) Thereafter, the plate is removed from the clamping fixture and the scribed ends are bent at right angles with. in some instances, heat applied to the plate to facilitate the bending operation. We have found that heating is advantageous when very small plate cylinders, of the order of 2-4" in diameter, are utilized.

(6) Finally, the plate is mounted on the plate cylinder and advantageously a lubricant may be applied to the sur face of the cylinder to insure conformity of the plate thereto.

While in the foregoing specification a detailed description of an embodiment of the invention has been set down for the purpose of explanation, many variations in the details herein given may be made by those skilled in the art without departing from the spirit and scope of the invention.

We claim:

1. A method of printing plate preparation, comprising elastically longitudinally stretching a plastic film substantially uniformly across its width adapted to be wrapped about a plate cylinder, scribing said film along a pair of spaced-apart transverse lines while said film is in stretched condition, folding said film on itself along said lines to develop insert flaps for said plate cylinder and thereafter mounting said film in enveloping relation on a plate cylinder with the fold lines engaging opposite sides of a longitudinal recess in the plate cylinder whereby substantially identical register in successive plates may be achieved.

2. The method of claim 1 in which said film is heated just prior to folding.

3. The method of claim 2 in which said film is a photopolymeric film and is heated to a temperature in the range of -200" F.

References Cited UNITED STATES PATENTS 2,589,022 3/1962 Page 264-320 2,027,314 1/1936 Heinlin 264-294 2,039,096 4/ 1936 Lukens 264-294 3,179,974 4/1965 Tonolo 18-1 3,184,787 5/1965 Steegmans 18-1 2,704,025 3/1955 Anderson et a1. 101-415.1 X 2,896,312 7/1959 Schell 29-407 X 3,126,825 3/1964 Tofano 101-4151 CHARLIE T. MOON, Primary Examiner. 

1. A METHOD OF PRINTING PREPARATION, COMPRISING ELASTICALLY LONGITUDINALLY STRETCHING A PLASTIC FILM SUBSTANTIALLY UNIFORMLY ACROSS ITS WIDTH ADAPTED TO BE WRAPPED ABOUT A PLATE CYLINDER, SCRIBING SAID FILM ALONG A PAIR OF SPACED-APART TRANSVERSE LINES WHILE SAID FILM ALONG A PAIR OF CONDITION, FOLDING SAID FILM ON ITSELF ALONG SAID LINES TO DEVELOP INSERT FLAPS FOR SAID PLATE CYLINDER AND THEREAFTER MOUNTING SAID FILM IN ENVELOPING RELATION ON A PLATE CYLINDER WITH THE FOLD LINES ENGAGING OPPOSITE SIDES OF A LONGITUDINAL RECESS IN THE PLATE CYLINDER WHEREBY SUBSTANTIALLY IDENTICAL REGISTER IN SUCCESSIVE PLATES MAY BE ACHIEVED. 